Capacitance of flat capacitor

Subject of this short elaboration is to designate a formula for capacitance of flat capacitor. The main reason for obtaining a mathematical formula for capacitance of flat capacitor is that it depends only from geometrical dimensions and material's constants. Flat capacitor's capacitance will be designated with application of following things:
• definition of electrical capacitance
• Gauss's law
• equation for electric flux
• dimensions of flat capacitor
• knowledge of material's constants → relative electrical permittivity and electrical permittivity of vacuum
• knowledge of electrical charge's density per area